Integrated circuits are formed on semiconductor substrates, or wafers. The wafers are then sawed into microelectronic dies, or semiconductor chips, with each die carrying a respective integrated circuit. Each semiconductor chip is mounted to a package, or carrier substrate, which is often mounted to a motherboard.
The completion of the integrated circuits involves numerous processing steps as well as the formation of various devices on the semiconductor substrate. Depending on the intended use of the semiconductor chip, one of the devices formed on the semiconductor substrate may be an inductor. Spiral inductors are often used in radio frequency (RF) devices and typically include a thin coil of metal formed over a dielectric material. During use, the inductors often experience inductive coupling with the semiconductor material in the substrate, which detrimentally affects the “quality factor,” or “Q factor,” of the inductor and thus impedes the performance of the device.
To minimize this coupling and increase the Q factor, the thickness of the dielectric layer below the inductor may be increased. However, regardless of the thickness of the dielectric, an appreciable amount of coupling still occurs. Attempts have also been made to create air cavities below the inductors, however the air cavities are not sealed and during subsequent processing steps, such as cleaning and sawing, the air cavity may be contaminated. Furthermore, it is difficult to control the size and shape of the air cavity. The air cavity often significantly decreases the mechanical strength of the semiconductor chip, and as a result, the semiconductor chip may be damaged during packaging or shipping. The thickness of the inductor coil may also be increased to reduce the electrical resistance of the inductor and thus increase the Q factor. However, increasing the thickness of the coil increases the size and adds to the manufacturing costs of the device.
Accordingly, it is desirable to increase the Q factor of the inductor without risking contamination. In addition, it is desirable to maintain sufficient mechanical strength in the semiconductor chip to withstand subsequent processing steps. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.